Passenger airliners commonly cruise at a height of about 35,000 feet above sea level, but maintain a pressure that exists at about 8,000 feet above sea level when the airliner flies above 8,000 feet. As a result, a person""s ears are subjected to pressure changes as the airliner ascends to about 8,000 feet and as the airliner descends from about 8,000 feet to sea level. In most people, their eustachian tube passes air between the environment and the inner ear so there is not a great pressure difference across the eardrum. However, in some people the eustachian tubes do not open sufficiently to allow air to be exchanged between the ambient environment and the middle ear. A result is a pressure differential across the eardrum and possible discomfort or pain. The discomfort or pain is experienced most acutely during airplane descent, when the cabin pressure increases from the pressure at about 8,000 feet above sea level to a pressure close to that at sea level. U.S. Pat. No. 5,467,784 describes an earplug with a bore extending between its opposite ends and with a pressure regulator lying along the bore, to very slowly pass air between the environment and the ear canal, so the rise in pressure in the ear canal is much slower than the rise in cabin pressure during a typical landing procedure. This provides time for air to leak through a person""s eustachian tube if the eustachian tube is only slightly open. Other earplug constructions which delayed the change in ear canal pressure, especially during the descent part of the flight, would be of value.
In accordance with one embodiment of the present invention, a pressure regulating earplug is provided which delays the change in pressure in the ear canal as the cabin pressure changes, especially during the descent portion of a flight when the cabin pressure rapidly increases. The earplug is of the type that has an earplug body with a front portion for entering an ear canal and a rear portion for grasping to pull the earplug out of the ear canal, with the front portion having a front end and having a sealing portion of largest diameter that seals against the ear canal. The earplug body has a cavity that is open to the front end of the body, and the earplug includes an a restrictor that allows the passage of air between the cavity and ear canal but at a restricted flow rate. The restrictor can be formed from porous material that is preferably foam material, and preferably with a foam material that has been compressed, or felted. The restrictor can restrict the rate of air flow out of the earplug cavity to the ear canal, or restrict the rate at which the cavity collapses.
As the cabin air pressure increases during airplane descent, the walls of the earplug surrounding the cavity deflect inwardly and help to expel air in the cavity so the air slowly passes into the ear canal. The rate of increase in ear canal pressure depends on the elasticity of the earplug material, thickness of cavity walls, cavity design, and possibly on the sealing flanges on the outside of the earplug.
The novel features of the invention are set forth with particularity in the appended claims. The invention will be best understood from the following description when read in conjunction with the accompanying drawings.